1. Field of the Invention
The present invention relates to cutting tools having a releasable and disposable cutting insert secured to an insert-receiving seat, including milling cutters and the like. Particularly, the present invention relates to a cutting tool having a positioning block between the cutting insert and the insert-receiving seat.
2. Prior Art
There are two basic types of insert-clamped cutting tools provided with the disposable cutting inserts.
For one type of conventional cutting tools, for example, a lever clamping type byte is depicted in FIG. 9. In this figure, the cutting tool comprises a tool body 1 having an insert-receiving seat or recess 2 formed at its forward end. The tool body 1 also has a L-shaped lever 3 provided in a hole opening to the insert-receiving seat 2 and a bolt 4 provided in a hole adjoined to the first hole. In this example, a throwaway cutting insert 6 with a mounting bore 7 formed therethrough is received on the insert receiving seat 2, while the L-shaped lever 3 is received in the first hole so as to protrude its head portion 5 from the seat 2 to engage with the mounting bore 7 of the insert 6 when the end portion of the lever 3 is pushed downwardly by the bolt 4. In this example, a positioning block 8 is provided between the insert 6 and the seat 2.
FIG. 10 depicts another type of the conventional insert-clamped cutting tool which comprises a tool body 10 having an insert receiving seat or recess 11 formed at its forward end and a bolt-receiving hole opening on the insert-receiving seat 11. A positioning block 12 with a bore formed therethrough is provided on the insert receiving seat 11, and a bolt 13 is inserted through the bore to engage the bolt therewith. Furthermore, a throwaway cutting insert 14 is mounted on the positioning block 12 and pressed against the seat 11 by clamping means including a clamp 15 and a clamping bolt 16.
In general, the positioning blocks 8 and 12 are made of materials such as cemented carbide, high speed steel or the like. Accordingly, these conventional blocks are characterized by their hardness which is lower than that of the cutting insert but higher than that of the surface of the seat to avoid wearing the insert down.
However, the conventional positioning block is made of hard material and thus it is difficult to absorb severe vibration of the cutting insert during the milling process. Consequently, the conventional cutting tool using the above described positioning block has some problems i.e., slipping off of the insert from the insert-receiving seat, damaging the cutting edge of the insert, chipping the insert, or the like, caused by the vibration of the cutting insert.